Examples of exercisers of these types are disclosed in U.S. Pat. Nos. 2,716,027, 3,117,782, 3,162,441, 3,834,694 and 3,858,874.
However, most previously known exercising machines are not capable of allowing one limb of a person exercising to function in opposition to another limb with both limbs in opposition opposing a variable weight load in one direction of movement. By such construction controlled exercising of a person's limbs may be carried out in an efficient manner and in a manner whereby the muscles being exercised may have the resistance loading thereon gradually increased throughout an extended period of muscle development through exercising.